Energy meters are used to record consumed or produced electrical energy. Such energy meters are also designated as current meters or kilowatt hour meters.
Normally speaking, tension and electricity are recorded, digitized and multiplied with one another in energy meters that are electronically operated. The current electrical power is ready following this multiplication. When this electrical power is integrated or accumulated over time, a signal is obtained which constitutes a measurement for the electrical energy that was generated or produced in a certain time interval.
Voltage dividers, voltage transformers or other means can be applied for signal extraction in order to obtain proportional signals for electrical voltage and electrical current.
It is for many applications essential that a galvanic isolation is to be provided in at least one of both chancels to record voltage and current. Such a galvanic isolation of the electric circuit prepares for instance a transformer.
However, the phase shift, which is caused by the inductive coupling of the transformer, is problematic in such transformers. On the one hand, the phase shift shows between the output signal and the input signal. On the other hand, the phase shift is also detected between the current and signal that represents the voltage. However, undesired measurement errors are caused as a result thereof when multiplying tension and current. It must hereby be observed that tension and current mostly do not exist as equal signals but rather as alternating current signals with a more or less harmonic signal form.
The described problems are additionally intensified by the fact that a non-exact predictable phase shift between both input channels can be caused by manufacturing tolerances, temperature effects, alteration effects or other unavoidable effects of a mass manufacturing even when a transformer-like transmitter is each time used in a voltage and current channel.
RC-networks, which comprise resistors and condensers, can for instance be used to correct the described undesired phase shift. However, these must usually be designed as additional external components and can normally not be integrated with disadvantages. Furthermore, the problems of the tolerances conditioned by the manufacturing and temperature are not fundamentally solved because of that.